Improvement in the methods of etching plates for electrotyping



To all whom it may concern:

preference brass, and after cleaning it we while still wet it is placedupon a level grat- UNITED STATES PATENT OFFICE.

ALFRED DAWSON AND HENRY T. DAWSON, OF OEDARS OHISWIGK, ASSIGN- ORS TOGEORGE WILLIAM PETTER AND THOMAS DIXON GALPIN, OF

LONDON, ENGLAND.

IMPROVEMENT IN THE METHODS OF ETCHlNG PLATES FOR ELECTROTYPING.

Specification forming part of Letters Patent No. 140,995, dated July 22,1873; application filed January 24, 1873.

Be it known that. we, ALFRED DAWSON and HENRY THOMAS DAWSON, both of theCedars Ohiswick, in the county of Middlesex, England, subjects of theQueen of Great Britain, have invented or discovered new and usefulImprovements in Typographic Etching and Engraving, and in apparatusemployed therein; and we, the said ALFRED DAWSON and HENRY THOMASDAWSON, do hereby declare the nature of the said invention, and in whatmanner the same is to be performed, to be particularly described andascertained in and by the following statement thereof; that is to say-This invention has for its object improvements in typographic etchingand engraving, and in apparatus employed therein. The inventionisdesigned to produce surface-printing blocks, in which the printingparts are in exact facsimile of the lines and marks made by the artistwhile drawing the design, and in which also there are deep curvedhollows between the raised lines and marks, which the paper in printingcannot enter, and which hollow spaces are so formed as to leave thelines so completely and perfectly buttressed up that no amount ofprinting-strain can crush or batter them down. In securing these ends weproceed as follows: We take a metal plate, by

darken and abrade or color the whole surface; this We prefer to do bymeans of a solution of a metallic salt, which acts on the metal plate soas both to remove the polish and darken the surface. .In practice, weuse a weak solution of nitrate of silver, containing, say, twenty grainsto the pint of water. The plate, which should be quite smooth, is washedand rubbed clean with a piece of pumice-stone;

ing and the silver solution poured upon it. It is distributed and movedover the plate with a soft brush until the surface has become dark allover, more solution being poured onto the plate if the first quantity isfound to be insufficient. A few minutes at the most is suflicient tocomplete this operation. The

plate is then washed with water and dried by warming it over a flame.When the plate is sufficiently Warm we cover it with an opaque, white,or light-colored ground; the plate is touched with the end of a thincake of the groundingcomposition, which is rapidly moved from place toplace on the plate, so as to leave a number of melted streaksdistributed pretty regularly all over the plate. The ground is thenspread by means of a warm or moderately-hot rake-like tool, consistingof a short rectangular brass bar, say two or threeinches long, with awire or stem fixed at right-angles to it and set in a handle. This toolis so applied to the plate as to touch it along one of its edges; and inthis edge of the tool a 11min ber of V-formed notches are filed at abouta tenth of an inch apart, so as to leave between them blunt-pointedteeth, between which the melted composition is able to flow freely. Thistool spreads the ground evenly when it is drawn to and fro over thesurface of the plate. The ground is afterward caused to flow sligh tlyover the plate by inclining it to and fro, which removes any marks leftby the teeth of the spreading-tool; the plate is then placed upon alevel support, and in a short time the ground sets firm. The thicknessof the ground should be about oneeightieth of an inch, more or less. Weuse a ground composition for the above purpose which is prepared fromsolid paraffineby grinding or mixing with it white or opaque color. Weemploy for this purpose the best paraffine, and we melt it and grind thepigment with it. The best pigment for the purpose we believe to betungstate of lead, and this we grind with the parafline in theproportion of three parts, by weight, of parafiiue to about one ofpigment. Or, if preferred, a tinted ground may be used, or even a blackground, but less conveniently. The

drawing is now made upon the plate by means of etching-points; and ifrepairs or alterations are needed'they can be made by means of a heatedtool. In drawing, we use several tools, some broad for clean cutting,like chisels or turning-tools; others have a fine point cut into severalfacets for neatly turning the shavings away from the work in twoor moredirections, according to the motion the point receives. The shavings areremoved by means of a badger-hair brush. Other tools are againconstructed for stamping or impressing the ground, common type beingfrequently thus used. The points for cutting the ground are used whenthe plate is cold; but when type or typelike tools are used, the plateshould be made warm to the temperature of 100 to 110 Fahrenheit, byholding it over a flame, or by laying it upon a plate with warm waterbeneath, taking care not to melt the composition.

he repair parts which are misdrawn by means of a small tool or wire,which is heated to the vaporizing-point of the paraffine (which adheresto it) in a smokeless flame, and applied to the plate so as to melt theground and cause it to flow over the false lines. If a large surfacerequires to be thus mended, little pieces of the ground composition maybe laid on the place, and melted by means of the repairing-tool. Aslight warmth in the plate is advantageous. Sometimes we purposely cutaway the ground, and afterward use a similar tool, but with a dividedpoint, like a mathematical pen, for containing a little melted ground,with which we then draw on the bare or nearly bare part of the plate,and lines and marks so made appear white in the print. In this way weare able to lay on lights, and produce an effect much admired by artistsand draftsmen.

Supposing, now, that the design required has been drawn upon the plate,and the artistic work complete, it will, on examination, be found thatthe grooves or spaces in the ground will vary much in sectional form,and in some cases there will be an overhanging of the groundingmaterial, and in other parts a burr or ridge of unremoved ground besidethe line.

To remove these irregularities, and to give an equal and similar form tothe sides of all the grooves or spaces in the ground, is the object ofthe next process, and it will always be found that if this is noteffected the printingblock made from the plate will give way after a fewhundred impressions have been taken from it. We apply heat in such amanner as to fuse the entire surface of the unremovcd ground, and so weremove all these irregularities and obtain the forms required. The formof fusion is always convex, and therefore always causes small arches inthe printing-block, and thus forms of great strength are given to theprinting parts. We effect this fusion by, as it were, brushing over thesurface of the plate with a gas-flame. The burner used is a plainperforation in the end of a closed metal tube attached to anIndia-rubber gas-pipe. The plate is laid on the hand, so that the degreeof warmth can be appreciated, and the flame is brushed to and fro manytimes over it while the plate is slightly warm, and until it is seenthat the surface has changed its form. If this operation be carefullyperformed, there is no fear of the ground running over the lines. Wethen build up the interspaces between the lines by applying a furtherquantity of paraffine by means of a heated tool. This tool is made on acapillary principle, so that it will hold the melted paraffine as a pendoes ink, and discharge it when its point is brought in contact with thework. We use a tool composed of anarrow coil of stout copper wire,through which pass two fine steel wires side by side, to form a hardpoint, and other wires or wedges for fastening the steel wires in thetool, as well as to form a number of capillary channels to hold andconduct the melted parafflne in the manner of a wick. The material Weuse is paraffine of a lower quality, and melting at a lower temperaturethan that for the ground, and it need contain no pigment. It is made upfor use into small sticks, with which the hot tool is touched from timeto time. Every particle of ground remaining on the plate exceeding a fewhundredths of an inch in length and width, is touched with thebuilding-up tool, and a small quantity of melted parat'tine depositedupon it.

Where the work is fine, care should be taken that the building'up toolis not too full, or the parafline may run out and injure the drawing.This having been done, in order more perfectly to unite the paraffinethus laid on with the ground beneath, and also to cause it to run up tothe edges of the lines and take forms of fusion, the plate is againbrushed over with the flame, in the manner already described. Thisbuildingup process is repeated once or twice, until the open parts ofthe drawing have been built up to a considerable height.

The plate having been thus completed, we lather it with yellow soap,applied with a badger-hair brush, and we then brush onto it, with asimilar brush, water which is rendered sour by the addition of muriaticacid. This treatment causes a thin film of grease to be deposited on thesurface of the ground. In this state, when dry, we send the plate to theelectrotyper, who first black-leads the surface with asoft brush, thenplaces it in his copperbath and starts the current immediately, havingfirst taken the usual precautions to expel air from the hollows. Thecopper plate produced is mounted in the usual way, for printing. Thedrawing being, by this process, (without any transfer or destructiveoperation,) made the foundation of a mold, the perfection 0f the worktells up afterward in all its integrity. The opaque matter being groundinto the grounding material, the effect of it remains, however thin orsmall are the particles of ground left on the plate. All parts of thedrawing being worked over, and the blackest parts being most workedupon, the small irregularities of surface which such work produces allprint in the'press, and this gives a great fullness and meaning to thedeepest shadows, none of which advantages can be obtained unless theprinting-face is an exact reproduction of a surface which has beenentirely produced by the drawing or etching point. The lines beingproduced by the point and not afterward altered have great smoothnessand freedom from granulation, or any other roughness. When a fine pointis used, great refinement of the work is obtained, so that the softestpossible grays may be faith fully printed in immediate contrast with thestrongest work.

Alterations can be made on the plate after an electrotype has beenremoved from it, in which case a new electrotype may be taken, embodyingthe said alterations.

The invention can be applied to many purposes in which engraving isexpensive or difficult, or imperfect, or slow, whether in art ormanufacture.

Having thus described the nature of our said invention, and the mannerof performing the same, we would have it understood that we claim- 1.The improvement in the art of producing a coated metallic design-platefor electrotyping, consisting of the following operations, viz: Theapplication of a fusible grounding composition to a metallic plate; themelting of the composition on the plate by heat, and the spreading of itwhile hot, so as to form a ground, which is permitted to harden; theremoval of portions of the ground by tools, so as to form the design ordrawing; the building up of the interspaces by the application of meltedmaterial; the remelting of the grounding composition by flame, toproduce the rounding of the edges, all substantially as before setforth.

2. The improvement in the art of producing a coated metallicdesign-plate for electrotyping, consisting of the following operations,viz:

The application of afusible grounding compo-

